Centrifugal compressor

ABSTRACT

A centrifugal compressor includes a motor cooling passage through which cooling fluid for cooling an electric motor flows, an air passage through which cooling air for cooling a first air bearing and a second air bearing is supplied to each of the first air bearing and the second air bearing, and a heat exchanger cooling the cooling air. The motor cooling passage includes a plurality of cooling axial passages having a first cooling axial passage through which the cooling fluid is supplied to the heat exchanger and a second cooling axial passage through which the cooling fluid is discharged from the heat exchanger. The heat exchanger has a first port communicating with the first cooling axial passage, a second port communicating with the second cooling axial passage, and a third port communicating with an air axial passage extending in an axial direction of a rotary shaft.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2021-170950 filed on Oct. 19, 2021, the entire disclosure of which isincorporated herein by reference.

BACKGROUND ART

The present disclosure relates to a centrifugal compressor. Acentrifugal compressor includes a rotary shaft, an electric motor, acompressor impeller, and a housing. The electric motor drives the rotaryshaft. The compressor impeller is rotated together with the rotary shaftto compress fluid. The housing has a motor chamber that accommodates theelectric motor. The centrifugal compressor includes a first air bearingand a second air bearing. The first air bearing and the second airbearing are arranged in the motor chamber. The first air bearing and thesecond air bearing are disposed on opposite sides of the electric motorin an axial direction of the rotary shaft to rotatably support therotary shaft. The housing has a circumferential wall that surrounds theelectric motor, a first end wall that closes one of opposite openingsformed on the circumferential wall, and a second end wall that closesthe other of the opposite openings formed on the circumferential wall.The circumferential wall, the first end wall, and the second end walldefine the motor chamber. The first end wall holds the first airbearing, and the second end wall holds the second air bearing, forexample.

The centrifugal compressor may include a motor cooling passage throughwhich cooling fluid for cooling the electric motor flows, as disclosedin Korean Patent Application Publication No. 10-2017-0088588. The motorcooling passage has a plurality of cooling axial passages extending inthe axial direction of the rotary shaft and spaced from each other alonga circumferential direction of the circumferential wall. In the motorcooling passage formed in the housing, the cooling axial passagesadjacent to each other along the circumferential direction of thecircumferential wall are connected. As a result, the motor coolingpassage efficiently extends along the circumferential direction of thecircumferential wall. Therefore, the electric motor surrounded by thecircumferential wall is efficiently cooled by the cooling fluid flowingthrough the motor cooling passage.

In the centrifugal compressor, heat is easily generated in each of thefirst air bearing and the second air bearing due to high-speed rotationof the rotary shaft. For example, International Publication No.2019/087869 discloses a centrifugal compressor including an air passagethrough which cooling air for cooling the first air bearing and thesecond air bearing is supplied to each of the first air bearing and thesecond air bearing. This kind of centrifugal compressor includes a heatexchanger configured to cool the cooling air by heat exchange betweenthe cooling air and the cooling fluid. The cooling air cooled in theheat exchanger is supplied to each of the first air bearing and thesecond air bearing through the air passage, so that the first airbearing and the second air bearing are efficiently cooled.

The air passage is required to have a structure in which the cooling airefficiently flows toward a part of the first end wall holding the firstair bearing and a part of the second end wall holding the second airbearing. Thus, the air passage needs to extend toward each of the firstend wall and the second end wall in the housing.

In the motor cooling passage formed in the housing, the cooling axialpassages adjacent to each other along the circumferential direction ofthe circumferential wall may be connected, as disclosed in Korean PatentApplication Publication No. 10-2017-0088588. In this case, the airpassage needs to be formed in the housing so as to extend toward each ofthe first end wall and the second end wall while avoiding the airpassage from interfering with the motor cooling passage. Thus, the airpassage needs to extend toward each of the first end wall and the secondend wall while bypassing the motor cooling passage, which may result inan increase in size of the centrifugal compressor.

SUMMARY

In accordance with an aspect of the present disclosure, there isprovided a centrifugal compressor including: a rotary shaft; an electricmotor that drives the rotary shaft; a compressor impeller that isrotated together with the rotary shaft to compress fluid; a housingincluding a motor chamber that accommodates the electric motor; a firstair bearing and a second air bearing disposed on opposite sides of theelectric motor in an axial direction of the rotary shaft to rotatablysupport the rotary shaft; a motor cooling passage through which coolingfluid for cooling the electric motor flows; an air passage through whichcooling air for cooling the first air bearing and the second air bearingis supplied to each of the first air bearing and the second air bearing;and a heat exchanger configured to cool the cooling air by heat exchangebetween the cooling air and the cooling fluid. The housing has acircumferential wall that surrounds the electric motor and has openingson opposite ends, a first end wall that closes one of the openings ofthe circumferential wall and holds the first air bearing, and a secondend wall that closes the other of the openings of the circumferentialwall and holds the second air bearing. The motor chamber is defined bythe circumferential wall, the first end wall, and the second end wall.The motor cooling passage includes a plurality of cooling axial passagesextending in the axial direction of the rotary shaft and spaced fromeach other along a circumferential direction of the circumferentialwall. The cooling axial passages adjacent to each other alongcircumferential direction of the circumferential wall are connected inthe motor cooling passage formed in the housing. The plurality ofcooling axial passages includes a first cooling axial passage throughwhich the cooling fluid is supplied to the heat exchanger and a secondcooling axial passage through which the cooling fluid is discharged fromthe heat exchanger. The air passage is formed between the first coolingaxial passage and the second cooling axial passage in the housing. Theair passage has an air axial passage extending in the axial direction ofthe rotary shaft toward each of the first end wall and the second endwall, and an air radial passage that communicates with the air axialpassage and through which the cooling air is supplied to the first airbearing and the second air bearing. The heat exchanger has a first portcommunicating with the first cooling axial passage, a second portcommunicating with the second cooling axial passage, and a third portcommunicating with the air axial passage. The heat exchanger is attachedto the housing such that the first port, the second port, and the thirdport overlap the first cooling axial passage, the second cooling axialpassage, and the air axial passage, respectively, on an outer side ofthe housing in a radial direction of the rotary shaft.

Other aspects and advantages of the disclosure will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with objects and advantages thereof, may bestbe understood by reference to the following description of theembodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional view for explaining a centrifugal compressoraccording to an embodiment;

FIG. 2 is an exploded perspective view schematically illustrating arelationship between a motor housing, a heat exchanger, and a secondradiator;

FIG. 3 is a schematic view illustrating a motor cooling passage and anair passage being modeled;

FIG. 4 is a front view of the heat exchanger;

FIG. 5 is a cross-sectional view for explaining a centrifugal compressoraccording to another embodiment; and

FIG. 6 is a front view of a heat exchanger according to anotherembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will describe an embodiment of a centrifugal compressorwith reference to FIGS. 1 to 4 . The centrifugal compressor of thepresent embodiment is mounted on a fuel cell vehicle.

Overall Configuration of Centrifugal Compressor 10

As illustrated in FIG. 1 , a centrifugal compressor 10 includes ahousing 11. The housing 11 is made of a metallic material, such asaluminum. The housing 11 has a motor housing 12, a compressor housing13, a turbine housing 14, a first plate 15, a second plate 16, and athird plate 17.

The motor housing 12 has a tubular shape. The motor housing 12 hasopenings on opposite ends thereof. The first plate 15 is connected toone end of the motor housing 12 and closes one of the openings of themotor housing 12. The second plate 16 is connected to the other end ofthe motor housing 12 and closes the other of the openings of the motorhousing 12.

The motor housing 12, the first plate 15, and the second plate 16 definea motor chamber 51. The motor chamber 51 accommodates an electric motor18. Thus, the housing 11 has the motor chamber 51. The motor housing 12serves as a circumferential wall surrounding the electric motor 18. Thefirst plate 15 serves as a first end wall that closes the one of theopenings of the motor housing 12. The second plate 16 serves as a secondend wall that closes the other of the openings of the motor housing 12.

The first plate 15 has a first bearing holding portion 20. The firstbearing holding portion 20 projects from a central portion of the firstplate 15 toward the electric motor 18. The first bearing holding portion20 has a cylindrical shape.

The first plate 15 has a chamber forming recess 15 a on an end surfaceof the first plate 15 that is opposite from the motor housing 12. Thechamber forming recess 15 a has a circular hole shape. An inner space ofthe first bearing holding portion 20 extends through the first plate 15and is opened at a bottom surface of the chamber forming recess 15 a.The chamber forming recess 15 a is formed coaxially with the firstbearing holding portion 20.

The second plate 16 has a second bearing holding portion 22. The secondbearing holding portion 22 projects from a central portion of the secondplate 16 toward the electric motor 18. The second bearing holdingportion 22 has a cylindrical shape.

The second plate 16 has a shaft insertion hole 16 a at the centralportion of the second plate 16. The shaft insertion hole 16 acommunicates with an inner space of the second bearing holding portion22. The shaft insertion hole 16 a is formed coaxially with the secondbearing holding portion 22.

The third plate 17 is connected to an end surface of the first plate 15that is opposite from the motor housing 12. The third plate 17 has ashaft insertion hole 17 a at a central portion of the third plate 17.The shaft insertion hole 17 a communicates with an inside of the chamberforming recess 15 a. The shaft insertion hole 17 a is formed coaxiallywith the chamber forming recess 15 a and the first bearing holdingportion 20. The third plate 17 and the chamber forming recess 15 a ofthe first plate 15 define a thrust bearing accommodating chamber S2. Thethrust bearing accommodating chamber S2 communicates with the innerspace of the first bearing holding portion 20. The thrust bearingaccommodating chamber S2 communicates with the shaft insertion hole 17a.

The compressor housing 13 has a tubular shape, and has an inlet 13 ahaving a circular hole shape from which air is drawn into the compressorhousing 13. The compressor housing 13 is connected to an end surface 17b of the third plate 17 that is opposite from the first plate 15 in astate in which the inlet 13 a is formed coaxially with the shaftinsertion hole 17 a of the third plate 17 and the first bearing holdingportion 20. The inlet 13 a is opened at an end surface of the compressorhousing 13 that is opposite from the third plate 17.

A first impeller chamber 13 b, a discharge chamber 13 c, and a firstdiffuser passage 13 d are formed between the compressor housing 13 andthe end surface 17 b of the third plate 17. The first impeller chamber13 b communicates with the inlet 13 a. The discharge chamber 13 cextends about the axis of the inlet 13 a around the first impellerchamber 13 b. The first impeller chamber 13 b communicates with thedischarge chamber 13 c through the first diffuser passage 13 d. Thefirst impeller chamber 13 b communicates with the shaft insertion hole17 a of the third plate 17. The compressor housing 13 has a dischargepassage 13 e that communicates with the discharge chamber 13 c.

The turbine housing 14 has a tubular shape, and has an outlet 14 ahaving a circular hole shape from which air is discharged from theturbine housing 14. The turbine housing 14 is connected to an endsurface 16 b of the second plate 16 that is opposite from the motorhousing 12 in a state in which the outlet 14 a is formed coaxially withthe shaft insertion hole 16 a of the second plate 16 and the secondbearing holding portion 22. The outlet 14 a is opened at an end surfaceof the turbine housing 14 that is opposite from the second plate 16.

A second impeller chamber 14 b, a suction chamber 14 c, and a seconddiffuser passage 14 d are formed between the turbine housing 14 and theend surface 16 b of the second plate 16. The second impeller chamber 14b communicates with the outlet 14 a. The suction chamber 14 c extendsabout the axis of the outlet 14 a around the second impeller chamber 14b. The second impeller chamber 14 b communicates with the suctionchamber 14 c through the second diffuser passage 14 d. The secondimpeller chamber 14 b communicates with the shaft insertion hole 16 a.

Configuration of Rotary Shaft 24

The centrifugal compressor 10 includes a rotary shaft 24. The housing 11accommodates the rotary shaft 24. The rotary shaft 24 has a shaft mainbody 24 a, a first supporting portion 24 b, a second supporting portion24 c, and a third supporting portion 24 d.

The shaft main body 24 a has a first end projecting into the firstimpeller chamber 13 b through the motor chamber 51, the inside of thefirst bearing holding portion 20, the thrust bearing accommodatingchamber S2, and the shaft insertion hole 17 a. The shaft main body 24 ahas a second end projecting into the second impeller chamber 14 bthrough the motor chamber 51, the inside of the second bearing holdingportion 22, and the shaft insertion hole 16 a. That is, the shaft mainbody 24 a extends through the motor chamber 51 along the axis of themotor housing 12. Therefore, an axial direction of the rotary shaft 24coincides with an axial direction of the motor housing 12.

The first supporting portion 24 b is disposed on a part of an outerperipheral surface of the shaft main body 24 a, closer to the first endthan a central portion of the shaft main body 24 a is. The firstsupporting portion 24 b is disposed inside the first bearing holdingportion 20. The first supporting portion 24 b is integrally formed withthe shaft main body 24 a. The first supporting portion 24 b projectsfrom the outer peripheral surface of the shaft main body 24 a.

The second supporting portion 24 c is disposed on a part of the outerperipheral surface of the shaft main body 24 a, closer to the second endthan the central portion of the shaft main body 24 a is. The secondsupporting portion 24 c is disposed inside the second bearing holdingportion 22. The second supporting portion 24 c is fixed to the outerperipheral surface of the shaft main body 24 a while annularlyprojecting from the outer peripheral surface of the shaft main body 24a. The second supporting portion 24 c is rotatable together with theshaft main body 24 a.

The third supporting portion 24 d is disposed on a part of the outerperipheral surface of the shaft main body 24 a, closer to the first endthan the first supporting portion 24 b is. The third supporting portion24 d is disposed inside the thrust bearing accommodating chamber S2. Thethird supporting portion 24 d is fixed to the outer peripheral surfaceof the shaft main body 24 a while annularly projecting from the outerperipheral surface of the shaft main body 24 a. The third supportingportion 24 d is rotatable together with the shaft main body 24 a.

A first sealing member 27 is disposed between the shaft insertion hole17 a of the third plate 17 and the rotary shaft 24. The first sealingmember 27 prevents leakage of the air flowing from the first impellerchamber 13 b toward the motor chamber S1. A second sealing member 28 isdisposed between the shaft insertion hole 16 a of the second plate 16and the rotary shaft 24. The second sealing member 28 prevents leakageof the air flowing from the second impeller chamber 14 b toward themotor chamber S1. Each of the first sealing member 27 and the secondsealing member 28 is a seal ring, for example.

Compressor Impeller 25

The centrifugal compressor 10 includes a compressor impeller 25. Thecompressor impeller 25 is connected to the first end of the shaft mainbody 24 a. The compressor impeller 25 is disposed at a part of the shaftmain body 24 a, closer to the first end of the shaft main body 24 a thanthe third supporting portion 24 d is. The compressor impeller 25 isaccommodated in the first impeller chamber 13 b. The compressor impeller25 is rotatable together with the shaft main body 24 a. Therefore, thecompressor impeller 25 is rotated together with the rotary shaft 24.

Turbine Wheel 26

The centrifugal compressor 10 includes a turbine wheel 26. The turbinewheel 26 is connected to the second end of the shaft main body 24 a. Theturbine wheel 26 is disposed at a part of the shaft main body 24 a,closer to the second end of the shaft main body 24 a than the secondsupporting portion 24 c is. The turbine wheel 26 is accommodated in thesecond impeller chamber 14 b. The turbine wheel 26 is rotatable togetherwith the shaft main body 24 a. Therefore, the turbine wheel 26 isrotated together with the rotary shaft 24.

Configuration of Electric Motor 18

The electric motor 18 includes a rotor 31 and a stator 32 each having atubular shape. The rotor 31 is fixed to the shaft main body 24 a. Thestator 32 is fixed to an inner peripheral surface of the motor housing12. The rotor 31 is disposed inside the stator 32 along a radialdirection thereof. The rotor 31 is rotated together with the shaft mainbody 24 a. The rotor 31 has a cylindrical rotor core 31 a fixed to theshaft main body 24 a and a plurality of permanent magnets (notillustrated) disposed in the rotor core 31 a.

The stator 32 surrounds the rotor 31. The stator 32 includes a statorcore 33 and a coil 34. The stator core 33 has a cylindrical shape and isfixed to the inner peripheral surface of the motor housing 12. The coil34 is wound around the stator core 33. When an electric current from abattery (not illustrated) flows through the coil 34, the rotary shaft 24is rotated together with the rotor 31. Thus, the electric motor 18drives the rotary shaft 24. That is, the electric motor 18 is a drivingpower source for rotating the rotary shaft 24. The electric motor 18 isdisposed between the compressor impeller 25 and the turbine wheel 26 inthe axial direction of the rotary shaft 24.

First Air Bearing 21 and Second Air Bearing 23

The centrifugal compressor 10 includes a first air bearing 21 and asecond air bearing 23. The first air bearing 21 has a cylindrical shape.The first air bearing 21 is held by the first bearing holding portion20. Therefore, the first plate 15 holds the first air bearing 21. Thefirst air bearing 21 is positioned closer to the first end of the shaftmain body 24 a than the electric motor 18 is. The first air bearing 21supports the first supporting portion 24 b.

The first air bearing 21 supports the rotary shaft 24 while being incontact with the first supporting portion 24 b until a rotational speedof the rotary shaft 24 reaches a levitation rotational speed at whichthe rotary shaft 24 is levitated by the first air bearing 21. When therotational speed of the rotary shaft 24 reaches the levitationrotational speed, the first supporting portion 24 b is levitated to thefirst air bearing 21 due to dynamic pressure of a pneumatic layergenerated between the first supporting portion 24 b and the first airbearing 21. Accordingly, the first air bearing 21 supports the rotaryshaft 24 without being in contact with the first supporting portion 24b.

The second air bearing 23 has a cylindrical shape. The second airbearing 23 is held by the second bearing holding portion 22. Thus, thesecond plate 16 holds the second air bearing 23. The second air bearing23 is positioned closer to the second end of the shaft main body 24 athan the electric motor 18 is. The second air bearing 23 supports thesecond supporting portion 24 c.

The second air bearing 23 supports the rotary shaft 24 while being incontact with the second supporting portion 24 c until the rotationalspeed of the rotary shaft 24 reaches a levitation rotational speed atwhich the rotary shaft 24 is levitated by the second air bearing 23.When the rotational speed of the rotary shaft 24 reaches the levitationrotational speed, the second supporting portion 24 c is levitated to thesecond air bearing 23 due to dynamic pressure of a pneumatic layergenerated between the second supporting portion 24 c and the second airbearing 23. Accordingly, the second air bearing 23 supports the rotaryshaft 24 without being in contact with the second supporting portion 24c. Therefore, the first air beating 21 and the second air bearing 23 aredisposed on opposite sides of the electric motor 18 in the axialdirection of the rotary shaft 24 to rotatably support the rotary shaft24.

Thrust Bearing 29

The thrust bearing 29 rotatably supports the rotary shaft 24 in a thrustdirection. The “thrust direction” corresponds to the axial direction ofthe rotary shaft 24. The thrust bearing 29 is disposed in the thrustbearing accommodating chamber S2. The thrust bearing 29 is an airbearing.

The thrust bearing 29 supports the rotary shaft 24 while being incontact with the third supporting portion 24 d until the rotationalspeed of the rotary shaft 24 reaches a levitation rotational speed atwhich the rotary shaft 24 is levitated by the thrust bearing 29. Whenthe rotational speed of the rotary shaft 24 reaches the levitationrotational speed, the third supporting portion 24 d is levitated to thethrust beating 29 due to dynamic pressure of a pneumatic layer generatedbetween the third supporting portion 24 d and the thrust bearing 29.Accordingly, the thrust bearing 29 supports the rotary shaft 24 withoutbeing in contact with the third supporting portion 24 d. Thus, thethrust bearing 29 rotatably supports the rotary shaft 24 in the thrustdirection. The thrust bearing 29 receives differential pressure betweenthe compressor impeller 25 and the turbine wheel 26.

Fuel Cell System 40

The centrifugal compressor 10 with the aforementioned configurationforms a part of a fuel cell system 40 that is mounted to the fuel cellvehicle. The fuel cell system 40 includes a fuel cell stack 41, a supplypassage 42, and a discharge passage 43, in addition to the centrifugalcompressor 10. The fuel cell stack 41 includes a plurality of fuelcells. The plurality of fuel cells is not illustrated for convenience ofdescription. The fuel cell stack 41 is connected to the dischargepassage 13 e through the supply passage 42. The fuel cell stack 41 isconnected to the suction chamber 14 c through the discharge passage 43.

When the rotary shaft 24 is rotated together with the rotor 31, thecompressor impeller 25 and the turbine wheel 26 are rotated togetherwith the rotary shaft 24. Then, air drawn from the inlet 13 a iscompressed by the compressor impeller 25 in the first impeller chamber13 b. Therefore, the compressor impeller 25 is rotated together with therotary shaft 24 to compress the air.

The air compressed in the first impeller chamber 13 b passes through thefirst diffuser passage 13 d and is discharged from the discharge chamber13 c. The air discharged from the discharge chamber 13 c is dischargedto the supply passage 42 through the discharge passage 13 e. The airdischarged to the supply passage 42 is supplied to the fuel cell stack41 through the supply passage 42. Thus, the centrifugal compressor 10supplies the air to the fuel cell stack 41. Oxygen contained in the airsupplied to the fuel cell stack 41 is useful for power generation of thefuel cell stack 41.

Here, the air supplied to the fuel cell stack 41 contains merely about20% of the oxygen being useful for the power generation of the fuel cellstack 41. Therefore, about 80% of the air supplied to the fuel cellstack 41 is discharged as a discharge gas from the fuel cell stack 41 tothe discharge passage 43 without being used for the power generation ofthe fuel cell stack 41. The discharge gas discharged to the dischargepassage 43 is drawn into the suction chamber 14 c through the dischargepassage 43. The discharge gas drawn into the suction chamber 14 c isintroduced into the second impeller chamber 14 b through the seconddiffuser passage 14 d. Then, kinetic energy of the discharge gasintroduced into the second impeller chamber 14 b is used to rotate theturbine wheel 26. As a result, the kinetic energy of the discharge gasis converted to rotational energy of the turbine wheel 26. Therotational energy generated in the turbine wheel 26 assists rotation ofthe rotary shaft 24. The discharge gas having passed through the secondimpeller chamber 14 b is discharged from the outlet 14 a to the outside.

Coolant Circuit 45

The fuel cell system 40 includes a coolant circuit 45. The coolantcircuit 45 has a pump 46, a first radiator 47, and a second radiator 48.Coolant (LLC: Long Life Coolant) circulates in the coolant circuit 45.The pump 46 pumps the coolant flowing in the coolant circuit 45. Thecoolant circulating in the coolant circuit 45 is cooled by heat exchangebetween the coolant inside the coolant circuit 45 and air outside thecoolant circuit 45 via the first radiator 47, when passing through thefirst radiator 47.

As illustrated in FIG. 2 , the motor housing 12 has an attaching surface121 to which the second radiator 48 is attached. FIG. 2 schematicallyillustrates the motor housing 12. The attaching surface 121 has a flatsurface shape. The second radiator 48 has one surface serving as anattachment surface 481 to be attached to the attaching surface 121 ofthe motor housing 12. The attachment surface 481 of the second radiator48 has a supply port 48 a and a discharge port 48 b.

Motor Cooling Passage 50, Air Passage 60, and Heat Exchanger 70

As illustrated in FIG. 1 , the centrifugal compressor 10 includes amotor cooling passage 50, an air passage 60, and a heat exchanger 70.Coolant serving as cooling fluid for cooling the electric motor 18 flowsthrough the motor cooling passage 50. Cooling air for cooling the firstair bearing 21 and the second air bearing 23 is supplied to each of thefirst air bearing 21 and the second air bearing 23 through the airpassage 60. The heat exchanger 70 is attached to the housing 11 in orderto cool the cooling air.

Configuration of Motor Cooling Passage 50

As illustrated in FIGS. 2 and 3 , the motor cooling passage 50 includesa plurality of cooling axial passages 51 extending in the axialdirection of the rotary shaft 24 inside the motor housing 12 and spacedfrom each other along a circumferential direction of the motor housing12. FIG. 3 illustrates the motor cooling passage 50 being modeled. Inthe motor cooling passage 50 formed in the housing 11, the cooling axialpassages 51 adjacent to each other along the circumferential directionof the motor housing 12 are connected.

Specifically, a recess 151 is formed on an end surface of the firstplate 15 close to the motor housing 12, as illustrated in FIG. 1 . Arecess 161 is formed on an end surface of the second plate 16 close tothe motor housing 12. As illustrated in FIG. 3 , the cooling axialpassages 51 adjacent to each other along the circumferential directionof the motor housing 12 are connected one another via the recess 151 ofthe first plate 15 and the recess 161 of the second plate 16.

The plurality of cooling axial passages 51 includes a first coolingaxial passage 52 through which the coolant is supplied to the heatexchanger 70 and a second cooling axial passage 53 through which thecoolant is discharged from the heat exchanger 70. The plurality ofcooling axial passages 51 includes a third cooling axial passage 54through which the coolant is supplied to the second radiator 48 and afourth cooling axial passage 55 through which the coolant is dischargedfrom the second radiator 48. The third cooling axial passage 54 and thefourth cooling axial passage 55 are arranged adjacent to each otheralong the circumferential direction of the motor housing 12.

The motor cooling passage 50 includes a first connecting passage 56 anda second connecting passage 57. The first connecting passage 56 and thesecond connecting passage 57 are formed in the motor housing 12. One endof the first connecting passage 56 communicates with the third coolingaxial passage 54. The other end of the first connecting passage 56 isopened at the attaching surface 121 of the motor housing 12. Then, theother end of the first connecting passage 56 communicates with thesupply port 48 a of the second radiator 48.

One end of the second connecting passage 57 communicates with the fourthcooling axial passage 55. The other end of the second connecting passage57 is opened at the attaching surface 121 of the motor housing 12. Then,the other end of the second connecting passage 57 communicates with thedischarge port 48 b of the second radiator 48.

The motor cooling passage 50 includes a cooling fluid supply passage 58and a cooling fluid discharge passage 59. The cooling fluid supplypassage 58 communicates with the second cooling axial passage 53. Thecoolant is supplied to the second cooling axial passage 53 through thecooling fluid supply passage 58. The cooling fluid discharge passage 59communicates with the first cooling axial passage 52. The coolant isdischarged from the first cooling axial passage 52 into the coolingfluid discharge passage 59.

Configuration of Air Passage 60

The air passage 60 includes an air axial passage 61. FIG. 3 illustratesthe air passage 60 being modeled. The air axial passage 61 is formed inthe motor housing 12. The air axial passage 61 is positioned between thefirst cooling axial passage 52 and the second cooling axial passage 53along the circumferential direction of the motor housing 12, and extendsin the axial direction of the rotary shaft 24 toward each of the firstplate 15 and the second plate 16.

The air passage 60 includes an air supply passage 62. The air supplypassage 62 communicates with the air axial passage 61. Specifically, theair supply passage 62 communicates with a part of the air axial passage61 that is closer to the second plate 16 than a central portion of theair axial passage 61 in the axial direction thereof is. The cooling airis supplied to the air axial passage 61 through the air supply passage62.

As illustrated in FIG. 1 , the air passage 60 includes a first airradial passage 63 and a second air radial passage 64 serving as an airradial passage that communicates with the air axial passage 61. Thecooling air is supplied to the first air bearing 21 through the firstair radial passage 63. The cooling air is supplied to the second airbearing 23 through the second air radial passage 64. The first airradial passage 63 is connected to one end of the air axial passage 61.The first air radial passage 63 extends in a radial direction of therotary shaft 24 inside the first plate 15. The first air radial passage63 communicates with the thrust bearing accommodating chamber S2. Thecooling air is supplied to the thrust bearing accommodating chamber S2through the first air radial passage 63.

The second air radial passage 64 is connected to the other end of theair axial passage 61. The second air radial passage 64 extends in theradial direction of the rotary shaft 24 inside the second plate 16. Thesecond air radial passage 64 communicates with the shaft insertion hole16 a. The cooling air is supplied to the shaft insertion hole 16 athrough the second air radial passage 64.

Air Discharge Passage 65

The centrifugal compressor 10 includes an air discharge passage 65. Oneend of the air discharge passage 65 communicates with the motor chamberS1. The other end of the air discharge passage 65 communicates with theoutlet 14 a of the turbine housing 14. The air discharge passage 65extends inside the second plate 16 and inside the turbine housing 14.The cooling air in the motor chamber S1 is discharged from the outlet 14a through the air discharge passage 65.

Attaching Surface 80

As illustrated in FIG. 2 , the motor housing 12 has an attaching surface80 to which the heat exchanger 70 is attached, on a part of the outerperipheral surface of the motor housing 12. The attaching surface 80 isa flat surface. The attaching surface 80 has an opening at which one endof the cooling fluid supply passage 58 opposite to the other end thereofin communication with the second cooling axial passage 53 is opened. Theattaching surface 80 has an opening at which one end of the coolingfluid discharge passage 59 opposite to the other end thereof incommunication with the first cooling axial passage 52 is opened. Theattaching surface 80 has an opening at which one end of the air supplypassage 62 opposite to the other end thereof in communication with theair axial passage 61 is opened. Thus, the cooling fluid supply passage58, the cooling fluid discharge passage 59, and the air supply passage62 are opened at the attaching surface 80. The attaching surface 80overlaps each of the first cooling axial passage 52, the second coolingaxial passage 53, and the air axial passage 61 on an outer side of themotor housing 12 in the radial direction of the rotary shaft 24.

Configuration of Heat Exchanger 70

The heat exchanger 70 has a flat square box shape. The heat exchanger 70is attached to the attaching surface 80 of the motor housing 12 using abolt (not illustrated), for example. The heat exchanger 70 cools thecooling air by heat exchange between the cooling air and the coolanthaving passed through the motor cooling passage 50. The heat exchanger70 has an attachment surface 70 a to be attached to the attachingsurface 80 of the motor housing 12.

As illustrated in FIG. 4 , a first port 71, a second port 72, and athird port 73 are opened at the attachment surface 70 a. The first port71 communicates with the cooling fluid discharge passage 59. Thus, thefirst port 71 communicates with the first cooling axial passage 52through the cooling fluid discharge passage 59. The second port 72communicates with the cooling fluid supply passage 58. Thus, the secondport 72 communicates with the second cooling axial passage 53 throughthe cooling fluid supply passage 58. The third port 73 communicates withthe air supply passage 62. Thus, the third port 73 communicates with theair axial passage 61 through the air supply passage 62. The heatexchanger 70 has a fourth port 74 that is opened on an end surface ofthe heat exchanger 70 opposite to the attachment surface 70 a. Asillustrated in FIG. 2 , a joint 75 is coupled to the fourth port 74. Thejoint 75 is a pipe bent into L-shape, for example.

Branch Pipe 90

As illustrated in FIG. 1 , the centrifugal compressor 10 includes abranch pipe 90. One end of the branch pipe 90 branches from a part ofthe discharge passage 13 e and extends outward from the compressorhousing 13. The other end of the branch pipe 90 opposite to thedischarge passage 13 e is connected to the joint 75. The one end of thebranch pipe 90 communicates with the discharge passage 13 e. The otherend of the branch pipe 90 communicates with the fourth port 74 of theheat exchanger 70 through the joint 75. A part of air passing throughthe discharge passage 13 e flows into the heat exchanger 70 through thebranch pipe 90, the joint 75, and the fourth port 74. Therefore, thecooling air passing through the heat exchanger 70 is a part of the aircompressed by the compressor impeller 25.

Operations

Next, the following will explain operations of the centrifugalcompressor according to the present embodiment.

The coolant passes through the inside of the heat exchanger 70 and isdischarged from the heat exchanger 70 into the cooling fluid supplypassage 58 through the first port 71. Then, the coolant passes throughthe cooling fluid supply passage 58 and is discharged into the secondcooling axial passage 53.

The coolant flows from the second cooling axial passage 53 to the thirdcooling axial passage 54 in the motor cooling passage 50. After that,the coolant having reached the third cooling axial passage 54 issupplied to the second radiator 48 through the first connecting passage56 and the supply port 48 a of the second radiator 48. The coolantsupplied to the second radiator 48 is cooled in the second radiator 48by heat exchange between the coolant in the second radiator 48 and thecoolant circulating in the coolant circuit 45.

The coolant cooled in the second radiator 48 is discharged from thesecond radiator 48 to the second connecting passage 57 through thedischarge port 48 b. The coolant discharged to the second connectingpassage 57 passes through the second connecting passage 57 and isdischarged to the fourth cooling axial passage 55 in the motor coolingpassage 50. The coolant flows from the fourth cooling axial passage 55toward the first cooling axial passage 52 in the motor cooling passage50. Then, the coolant having reached the first cooling axial passage 52is supplied to the heat exchanger 70 through the cooling fluid dischargepassage 59 and the second port 72. The coolant flows through the motorcooling passage 50 as described above, so that the electric motor 18surrounded by the motor housing 12 is cooled by the coolant flowingthrough the motor cooling passage 50.

A part of the air passing through the discharge passage 13 e flows intothe heat exchanger 70 through the branch pipe 90, the joint 75, and thefourth port 74 and serves as the cooling air for cooling the first airbearing 21 and the second air bearing 23. The cooling air passingthrough the heat exchanger 70 is cooled by heat exchange between thecooling air and the coolant passing through the heat exchanger 70. Then,the cooling air having passed through the heat exchanger 70 flows intothe air supply passage 62 through the third port 73. The cooling airhaving flowed into the air supply passage 62 flows toward both the firstplate 15 and the second plate 16 through the air axial passage 61. Thecooling air flowing toward the first plate 15 through the air axialpassage 61 corresponds to a first cooling air, and the cooling airflowing toward the second plate 16 through the air axial passage 61corresponds to a second cooling air.

The first cooling air flowing toward the first plate 15 through the airaxial passage 61 flows into the first air radial passage 63. The firstcooling air flowing through the first air radial passage 63 is suppliedinto the thrust bearing accommodating chamber S2. The first cooling airsupplied into the thrust bearing accommodating chamber S2 cools thethrust bearing 29. Then, the first cooling air having cooled the thrustbearing 29 flows into the first bearing holding portion 20 and issupplied to the first air bearing 21 to cool the first air beating 21.The first cooling air having cooled the first air bearing 21 flowstoward the air discharge passage 65 while cooling the electric motor 18in the motor chamber S1.

On the other hand, the second cooling air flowing toward the secondplate 16 through the air axial passage 61 flows toward the second airradial passage 64. The second cooling air flowing through the second airradial passage 64 is supplied into the shaft insertion hole 16 a. Thesecond cooling air supplied into the shaft insertion hole 16 a flowsinto the second bearing holding portion 22 and is supplied to the secondair bearing 23 to cool the second air bearing 23. The second cooling airhaving cooled the second air bearing 23 flows toward the air dischargepassage 65 in the motor chamber S1. The second cooling air in theelectric motor 18 passes through the air discharge passage 65 and isdischarged from the outlet 14 a to the outside. As described above, thethrust bearing 29, the first air bearing 21, and the second air bearing23 are cooled by the first cooling air and the second cooling air,respectively.

Effects

The aforementioned embodiment provides following advantageous effects.

(1) The air axial passage 61 of the air passage 60 is positioned betweenthe first cooling axial passage 52 and the second cooling axial passage53 and extends in the axial direction of the rotary shaft 24 toward eachof the first plate 15 and the second plate 16. As a result, the airpassage 60 need not extend toward each of the first plate 15 and thesecond plate 16 while bypassing the motor cooling passage 50, whichdownsizes the centrifugal compressor 10. Then, the first cooling air andthe second cooling air having flowed through the air axial passage 61are supplied to the first air bearing 21 and the second air bearing 23through the first air radial passage 63 and the second air radialpassage 64, respectively, so that the first air bearing 21 and thesecond air bearing 23 are efficiently cooled by the first cooling airand the second cooling air. The heat exchanger 70 is attached to themotor housing 12 such that the first port 71, the second port 72, andthe third port 73 overlap the first cooling axial passage 52, the secondcooling axial passage 53, and the air axial passage 61, respectively, onan outer side of the motor housing 12 in the radial direction of therotary shaft 24. The aforementioned configuration downsizes thecentrifugal compressor 10.

(2) The cooling fluid supply passage 58, the cooling fluid dischargepassage 59, and the air supply passage 62 are opened at the attachingsurface 80 of the motor housing 12. The first port 71 communicating withthe cooling fluid discharge passage 59, the second port 72 communicatingwith the cooling fluid supply passage 58, and the third port 73communicating with the air supply passage 62 are opened at theattachment surface 70 a of the heat exchanger 70. Accordingly, thelength of each of the cooling fluid supply passage 58, the cooling fluiddischarge passage 59, and the air supply passage 62 is shortened as muchas possible. As a result, the aforementioned configuration furtherdownsizes the centrifugal compressor 10.

(3) The cooling air passing through the heat exchanger 70 is a part ofthe air compressed by the compressor impeller 25. Accordingly, a part ofthe air compressed by the compressor impeller 25 is used as the firstcooling air and the second cooling air for cooling the first air bearing21 and the second air bearing 23, respectively. Thus, air that differsfrom the air compressed by the compressor impeller 25 need not besupplied to each of the first air bearing 21 and the second air bearing23 through the air passage 60 while serving as the first cooling air andthe second cooling air for cooling the first air bearing 21 and thesecond air bearing 23, respectively. As a result, a configuration inwhich the first air bearing 21 and the second air bearing 23 are cooledcan be simplified.

Modifications

The aforementioned embodiment may be modified as follows. The embodimentmay be combined with the following modifications within technicallyconsistent range.

As illustrated in FIG. 5 , the housing 11 may have an air branch passage91 through which a part of the air compressed by the compressor impeller25 flows. The air branch passage 91 is opened at the attaching surface80. As illustrated in FIG. 6 , the attachment surface 70 a of the heatexchanger 70 has a fourth port 92 that communicates with the air branchpassage 91. The air flowing through the air branch passage 91 passesthrough the inside of the heat exchanger 70 via the fourth port 92 whileserving as cooling air for cooling the first air bearing 21 and thesecond air bearing 23. Therefore, the cooling air passing through theheat exchanger 70 is a part of the air corresponding to fluid compressedby the compressor impeller 25.

Accordingly, a part of the air compressed by the compressor impeller 25is used as the cooling air for cooling the first air bearing 21 and thesecond air bearing 23. Thus, air that differs from the air compressed bythe compressor impeller 25 need not be supplied to each of the first airbearing 21 and the second air bearing 23 through the air passage 60while serving as the cooling air for cooling the first air bearing 21and the second air bearing 23. As a result, a configuration in which thefirst air bearing 21 and the second air bearing 23 are cooled can besimplified. The housing 11 has the air branch passage 91 that is openedat the attaching surface 80 and through which a part of the aircompressed by the compressor impeller 25 flows. The attachment surface70 a has the opening corresponding to the fourth port 92 thatcommunicates with the air branch passage 91. The aforementionedconfiguration shortens the length of the air branch passage 91 as muchas possible and further downsizes the centrifugal compressor 10.

In the aforementioned embodiment, air that differs from the aircompressed by the compressor impeller 25 may be supplied to each of thefirst air bearing 21 and the second air beating 23 through the airpassage 60 while serving as the cooling air for cooling the first airbearing 21 and the second air bearing 23.

In the aforementioned embodiment, a shape of the heat exchanger 70 isnot limited to the flat square box shape.

In the aforementioned embodiment, the supply port 48 a and the dischargeport 48 b need not be formed on the attachment surface 481 of the secondradiator 48, but may be formed on a surface other than the attachmentsurface 481 of the second radiator 48. That is, the supply port 48 a andthe discharge port 48 b may be formed in the second radiator 48 at anyopening positions as long as the first connecting passage 56communicates with the supply port 48 a and the second connecting passage57 communicates with the discharge port 48 b.

In the aforementioned embodiment, the cooling axial passages 51 and theair axial passage 61 need not be completely parallel to the axialdirection of the rotary shaft 24, and may bend or extend diagonally inthe axial direction of the rotary shaft 24 within a predeterminedtolerance.

In the aforementioned embodiment, the first air radial passage 63 andthe second air radial passage 64 need not be completely parallel to theradial direction of the rotary shaft 24, and may bend or extenddiagonally in the radial direction of the rotary shaft 24 within apredetermined tolerance.

In the aforementioned embodiment, the centrifugal compressor 10 ismounted to a fuel cell vehicle and is used for supplying air to the fuelcell stack 41, but the centrifugal compressor 10 may be used for avehicle air conditioner and may be configured to compress refrigerant asfluid, for example. The centrifugal compressor 10 may be mounted toanything other than the vehicle.

What is claimed is:
 1. A centrifugal compressor comprising: a rotaryshaft; an electric motor that drives the rotary shaft; a compressorimpeller that is rotated together with the rotary shaft to compressfluid; a housing including a motor chamber that accommodates theelectric motor; a first air bearing and a second air bearing disposed onopposite sides of the electric motor in an axial direction of the rotaryshaft to rotatably support the rotary shaft; a motor cooling passagethrough which cooling fluid for cooling the electric motor flows; an airpassage through which cooling air for cooling the first air bearing andthe second air bearing is supplied to each of the first air bearing andthe second air bearing; and a heat exchanger configured to cool thecooling air by heat exchange between the cooling air and the coolingfluid, the housing having a circumferential wall that surrounds theelectric motor and has openings on opposite ends, a first end wall thatcloses one of the openings of the circumferential wall and holds thefirst air bearing, and a second end wall that closes the other of theopenings of the circumferential wall and holds the second air bearing,the motor chamber being defined by the circumferential wall, the firstend wall, and the second end wall, the motor cooling passage including aplurality of cooling axial passages extending in the axial direction ofthe rotary shaft and spaced from each other along a circumferentialdirection of the circumferential wall, the cooling axial passagesadjacent to each other along the circumferential direction of thecircumferential wall being connected, in the motor cooling passageformed in the housing, wherein the plurality of cooling axial passagesincludes a first cooling axial passage through which the cooling fluidis supplied to the heat exchanger and a second cooling axial passagethrough which the cooling fluid is discharged from the heat exchanger,the air passage has an air axial passage being positioned between thefirst cooling axial passage and the second cooling axial passage in thehousing and extending in the axial direction of the rotary shaft towardeach of the first end wall and the second end wall, and an air radialpassage that communicates with the air axial passage and through whichthe cooling air is supplied to the first air bearing and the second airbearing, the heat exchanger has a first port communicating with thefirst cooling axial passage, a second port communicating with the secondcooling axial passage, and a third port communicating with the air axialpassage, and the heat exchanger is attached to the housing such that thefirst port, the second port, and the third port overlap the firstcooling axial passage, the second cooling axial passage, and the airaxial passage, respectively, on an outer side of the housing in a radialdirection of the rotary shaft.
 2. The centrifugal compressor accordingto claim 1, wherein the motor cooling passage includes: a cooling fluiddischarge passage to which the cooling fluid is discharged from thefirst cooling axial passage; and a cooling fluid supply passage throughwhich the cooling fluid is supplied to the second cooling axial passage,the air passage includes an air supply passage through which the coolingair is supplied to the air axial passage, a part of an outer peripheralsurface of the circumferential wall is an attaching surface to which theheat exchanger is attached, the cooling fluid supply passage, thecooling fluid discharge passage, and the air supply passage are openedat the attaching surface, the heat exchanger has an attachment surfaceto be attached to the attaching surface of the housing, and the firstport communicating with the cooling fluid discharge passage, the secondport communicating with the cooling fluid supply passage, and the thirdport communicating with the air supply passage are opened at theattachment surface of the heat exchanger.
 3. The centrifugal compressoraccording to claim 2, wherein the cooling air passing through the heatexchanger corresponds to a part of air compressed by the compressorimpeller, the housing has an air branch passage that is opened at theattaching surface of the housing and through which a part of the aircompressed by the compressor impeller flows, and a fourth port isfurther opened at the attachment surface of the heat exchanger andcommunicates with the air branch passage.